Listen fans had had enough of the guy, year upon year of the same rubbish, no progression, collapse after collapse, never getting rid of deadwood, letting top players walk out for nothing, sticking to the same system time and time again even when it wasn't working, abandoning all the things that made him sucessful in the 1st place, reluctance to spend money and when he did the majority of the time he insisted on trying to find the next big thing rather than signing a proven player, refusing to sign a DM and for years an out and out striker, harping on about top 4 being a major trophy, despite getting humiliated in the competition time and time again, choosing to criticise the fans rather than his own playing staff, is it any surprise people grew frustrated and called him the worst manager around and that anyone would do better? Sometime people say thing when they're angry/frustrated that aren't always gospel truth, the point was the man was driving the fans nuts with his stubborness.
The fact noone would have him back, even now probably tells you everything you need to know, even when things are bad we wouldn't choose to have him in charge, in fact at the moment it seems like no club does as he hasn't managed since he left us
The squad was awful, not being funny but look at the players we got left with, defenders that can't defend, midfielders that were average, other than the two strikers (neither of which he wanted particularly it seemed - Lacazette he barely played and Aubameyang there was talk was signed despite him being reluctant) it had very little quality, the only difference is we had a big suqad which allowed us to rest players, something the smaller clubs don't have, thus injuries/tiredness has a much great impact on their ability to last the distance, in addition the smaller clubs didn't have top strikers like we did and that's often the difference between no points and 3 points at this level.